No, this is not part of the "Wayward Children" series, but you can see the same author is weaving with some of the same threads, as she's making a new pattern. This book pulled me in and I swept through it, enjoying the ride. Some of McGuire's common bits, like alternate world fairy tales, special children, magic, etc., are present. However, she also brings in alchemy and ideas from the period when early science and magic still had a large overlap in the psyche of human civilization.
Mild spoiler: In this case, she explores what is might be like if universal forces were incarnated as children, paradoxes, etc. We might even see the birth of a new pantheon, of sorts.